In general, the structure of any given valve assembly is greatly dictated by the conditions of intended use. In particular, the amount of back pressure likely to be encountered, the nature of the flowable medium to be controlled, the temperature of the system, the temperature fluctuations likely to be encountered by this system, the presence or absence of particulate material in the flow to be controlled, the power source available for control of the valve, size and space limitations, whether or not the conditions of use will likely subject the components of the assembly to substantial shock or vibration, and similar variables on conditions of use will dictate advantage and disadvantage to various valve assembly designs, for use in any given system. In addition, economic factors, such as cost and availability of components, will also dictate valve construction in certain uses. Further, the amount of leakage which can be tolerated and the likelihood and effect of pressure surges, with respect to the process being controlled by the valve assembly, will in part dictate limitations on the type or construction of valve. The amount of "valve stick" that can be safely tolerated; whether the valve is normally maintained "open" or "closed" in use; and, the geometric tolerances of the system, are also factors which effect valve design.
In certain applications, poppet valve assemblies are used. A schematic generally indicating a conventional poppet valve assembly is shown in FIG. 1. Referring to FIG. 1, poppet valve assembly 5 comprises poppet valve member 6 and valve seat 7. In use, the poppet valve member 6 is biased against the valve seat 7, in sealing relation, when it is desired to close fluid flow through aperture 9, defined by the valve seat 7. Such a system might be used, for example, for controlling air or exhaust gas flow.
More specifically, poppet valve 6 comprises a shaft or stem 12 and valve head 13. Valve head 13 is sized and configured for mating with aperture 9 in a sealing fashion, during use. The stem 12 is used to direct the valve head 13, selectively, into and out of sealing relationship with aperture 9. The stem 12 is movably mounted, for example by being slidably received within bushing 15, to operationally direct the valve head 13. A variety of means may be utilized to direct or control movement of the stem 12 and valve head 13, the embodiment shown in FIG. 1 utilizing actuator 19.
In conventional poppet valve arrangements such as that shown in FIG. 1, a variety of means have been utilized to accomplish the sealing relationship between the valve head 13 and the aperture 9. In some instances either the valve head 13, the aperture 9 of the valve seat 7, or both, are provided (lined) with a soft compressible material such as a polymeric material, for formation of a seal under pressure with the other component. In other instances, relatively hard, non-compressible materials such as metal, machined for precise sealing engagement have been used for the valve head 13 and valve seat 7. The assembly shown in FIG. 1 involves utilization of a steel head 25 precisely machined along frusto-conical surface 26 for snug, sealing, relationship with recessed surface 28 of valve seat 7.
The conventional poppet valve assembly 5 of FIG. 1 is shown constructed such that stem 12 is selectively biased toward valve seat 7, when it is desired that aperture 9 be closed to fluid flow therethrough. Alternate systems, for example in which the stem is biased away from the aperture during use, are known. One such conventional system is illustrated in FIG. 2.
Referring to FIG. 2, valve assembly 30 comprises poppet valve member 31 and valve seat 32. Valve seat 32 is defined by aperture 35, which allows flow of fluid therethrough when the valve is open. Poppet valve member 31 comprises stem 37 with head 38 mounted thereon. For the arrangement shown in FIG. 2, the stem 37 is shown slidably mounted in bushing 40 for selective positioning relative to seat 32. Movement of stem 37, selectively, for opening and closing of aperture 35 is generated by a biasing arrangement 42. For the illustration in FIG. 2 the biasing arrangement 42 comprises actuator 43.
The valve assembly 30 operates for closure upon movement of the stem 37 in a direction opposite to that of the arrangement 5 shown in FIG. 1. In particular, aperture 35 is closed when stem 37 is manipulated to pull head 38 into seat 32. Similar means, for providing the sealing relationship between the head 38 and the valve seat 32, may be used for assembly 30 of FIG. 2 as were described above with respect to assembly 5 of FIG. 1.
It is noted that conventional poppet valve assemblies such as those shown in FIGS. 1 and 2 are known for use in systems wherein fluid flow is in either direction with respect to the aperture. That is, for example referring to FIG. 1 showing poppet valve assembly 5, such systems have been utilized to close aperture 9 to passage of fluid flow therethrough, when the pressure of the fluid flow is from either direction; i.e., both when the sealing pressure on the valve head 13 applied by the stem 12 is against the direction of the fluid flow and also when the sealing pressure is in the same direction as fluid flow.
The present invention concerns a particular poppet valve assembly, described hereinbelow, which addresses certain types of problems that can arise if a conventional poppet valve assembly such as that generally described with respect to FIGS. 1 and 2 were utilized in certain circumstances. A particular application of use, i.e., in association with a particulate trap for diesel exhaust, is described in detail hereinbelow.